A bit late to respond, but...
My 1990 K75s had the pipe through the steering stem. It was a non-ABS model.
My 1992 K75s had ABS - and it had a single flexline to the RH caliper, and the solid line arcing over the wheel to the LH caliper.
FWIW - I deleted the non-working ABS from the 1992 and moved all the non-ABS components (and forks and triple-clamps) to my 1992 "keeper."
As for missing parts, Laitch, the PO of the 1990 had run new lines from the downpipe directly to the front calipers, and had eliminated the hard lines. When I got the apparently too-short lines for the 1990, I assumed Spiegler had made an error, but then I learned that I was missing parts, not them.